1. Field of the Invention
The present invention generally relates to an apparatus to warm a liquid to a predetermined temperature. More specifically, the present invention relates to a system to warm a liquid to a desired temperature prior to the introduction of this fluid into the body.
2. Description of the Prior Art
Fluid introduced intravenously should be warmed to a temperature approximating body temperature to prevent the lowering of core body temperatures. Some intravenous fluids are shelf stable and are stored at ambient temperatures which are very often 75.degree. F. or below (more than 20.degree. F. below normal body temperature). Other intravenous fluids must be stored at refrigerated temperatures in the 32.degree. F. to 40.degree. F. range (more than 50.degree. F. below core temperature). In emergency situations, such intravenous fluids may necessarily be introduced at refrigerated temperatures directly into the body through I.V. tubes. Introduction of such liquids at these refrigerated temperatures, however, presents a substantial risk for injurious chill or shock to the body.
A variety of devices have been developed to address the issue of the warming of intravenous fluids. Current systems are generally of two types. Bulk warmers require a significant period of time to warm the product to a desired temperature. Moreover, in order for the bulk warmer to be constantly ready for emergency use, it must be maintained at a proper and set temperature. Such a maintenance procedure, however, is not possible for certain blood products and pharmaceuticals which will degrade if maintained at an elevated temperature.
Moreover, the bulk warmers allow the fluid to cool in the line set as it is administered. This system therefore also experiences drawbacks associated with emergency use since it requires prior anticipation of the need for warmed units as well as the number of units which will ultimately be needed. Furthermore, and assuming the aforereferenced conditions are met, units which are warmed and ready for use must move through several feet of tubing in addition to the drip chamber, thereby offering substantial time and opportunity for such liquids to cool before entering the body.
Previous in-line fluid warmers somewhat address the disadvantages described above except that such in-line systems attempt to warm the fluid in the existing plastic line set which is an inefficient means of heat transfer. Moreover, in-line warming systems are limited in volume, e.g. 30-40 millimeters per minute, and require a 120 volt A/C power source. Additionally, the accuracy of such system is only plus or minus 5 degrees.